A number of automated or semi-automated book scanning or reading systems are presently known in the art of book imaging, recording, and electronic archiving. In the use of such systems, a book is typically held in an open state, and a digital image of each page in sequence is acquired through either a digital camera, or an LED based scanner. One main function of such systems is to turn, and thereby expose to an imaging system, every page of a book in sequence.
It will be appreciated that a book or similar document reading system must overcome various problems. It is particularly desirable that a book reading system be capable of reading a large majority of books that are candidates for conversion to electronic format. For example, such a book reading system has utility in public and university libraries. Accordingly, a book reading system in such an application must be able to reliably read books with a wide range of physical properties or characteristics, without damaging such books.
Among the properties and conditions that an optimal book reading apparatus must accommodate are the following:                a) Physical size, i.e. the length and width of the book leaves, and the book cover board, if present.        b) Physical thickness of the book, i.e. substantially the number of leaves of the book, times the thickness of each page.        c) The thickness and paper composition of each leaf, and the properties related thereto (e.g., mass, stiffness, porosity, and the like).        d) The existence and characteristics such as elasticity of the book spine, i.e. whether the book spine remains flat when the book is opened, or whether it forms an arch, and to what extent it arches (radius of curvature). Alternatively, the leaves (pages) may be “bound” in a three-ring binder, or may simply be loosely assembled together without a binding.        e) The stiffness and support properties of the cover board on a hardcover book, versus the absence thereof on a paperback book.        f) The presence of anomalies in the structure of the book, such as a broken, creased, or split binding, rough-edged leaves, or other wear-and-tear, which result in variation in the properties of the book from leaf to leaf. Such anomalies would be considered as a source of noise in the art of statistical process control.        g) Variation in ambient conditions, such as relative humidity, which result in variability in the properties of the leaf paper, due to moisture absorption and desorption. Such variability would also be a source of noise to be accommodated by the book reading apparatus.        
In addition to accommodating the variability from book-to-book, an automated book reading apparatus must also accommodate the variation in page location during the transition of open page location from the front of the book, to the back of the book. If an open book is held with its front and back covers in a fixed position, and the pages are sequentially turned, the physical location of the open pages will change due to the cumulative effect of the leaves being displaced from one side of the book to the other side, and also due to variation in leaf curvature, with respect to open page location.
Heretofore, a number of patents and patent applications have disclosed apparatus for book positioning and/or page turning, used in book reading, imaging, and recording, the relevant portions of which are hereby incorporated by reference for their teachings, and which may be briefly summarized as follows:
U.S. Pat. No. 6,264,188 B1 to Taylor et al, issued Jul. 24, 2001, discloses a sheet feeding apparatus having an adaptive air fluffer and an air plenum, which operate together to separate a top sheet from a stack of sheets therebelow.
U.S. Pat. No. 6,279,896 B1 to Linder et al, issued Aug. 28, 2001, discloses a sheet feeding apparatus including a vacuum source that is selectively actuable, a translating vacuum feed head attached to the vacuum source to acquire the top sheet of the stack, a unidirectional rotating drive mechanism, and a control circuit, which dynamically adjusts vacuum and positive pressures to ensure proper sheet feeding.
U.S. Pat. No. 6,398,206 B1 to Taylor et al, issued Jun. 4, 2002, discloses a sheet feeding apparatus having an air plenum with a corrugated surface, comprising a first set of ribs at a first height and a second set of ribs at a second height, which corrugates and separates a top paper sheet from a stack of paper sheets therebelow, regardless of the weight of the paper stock of the sheets.
U.S. Pat. No. 6,398,208 B1 to Taylor et al, issued Jun. 4, 2002, discloses a sheet feeding apparatus having an air plenum with a corrugated surface and with a leaky perimeter seal, which corrugates and separates a top paper sheet from a stack of paper sheets and seals thereto.
Some aspects of the present invention are directed to the application of a vacuum plenum having a corrugated surface as an aid to the separation and turning of pages in an open-book scanner. Scanners of the type in which the present application find a particular use are described, for example, in the following patents U.S. Pat. No. 6,056,258, U.S. Pat. No. 5,640,252 and U.S. Pat. No. 5,359,207. These patents and applications are hereby incorporated by reference into this specification for their teachings related to page turning, scanning and/or vacuum handling of paper sheets and pages.